1. Field of Invention
The present invention relates to a method for objectively evaluating quality of stereo image, and more particularly to a digital watermarking based method for objectively evaluating quality of stereo image.
2. Description of Related Arts
With the rapid development of communication technology and multimedia technology, stereo image processing technology is gradually applied in various fields such as three-dimensional video conference system, virtual reality, remote industrial control, distance education and medical treatment, automatic navigation and consumer electronics. In a stereo image compression or transmission system, the quality of the compressed or transmitted stereo image is often utilized for evaluating the advantages and disadvantages of the system or adjusting the relative parameters thereof, so as to achieve a better compression or transmission effect. Since human beings are the final receiver of the stereo image, the subjective evaluation of the stereo image by the human beings is considered to be the most reliable. However, the subjective evaluation of the stereo image can not be described with a mathematical model and is easily influenced and restricted by other factors, and thus is not suitable for engineering application. Objectively evaluating quality of the stereo image is alternative method for this purpose. According to the dependence on the original stereo image, the methods for objectively evaluating stereo image are classified into three categories: FR (Full Reference), RR (Reduced-Reference) and NR (No Reference). The full reference method for objectively evaluating stereo image needs an integrated original stereo image for reference, and is suitable for design of stereo image encoder and performance comparison between different stereo image encoders. The no reference method for objectively evaluating stereo image needs no original stereo image for reference, and is mainly utilized for evaluating known degradation of images such as blocking effect, ringing effect and fuzzy distortion, and thus the application thereof is greatly limited. By contrast, the reduced-reference method for objectively evaluating stereo image is a method between the full reference method and the no reference method. The reduced-reference method takes advantage of part of the characteristic information of the reference stereo image for evaluating perceived quality of distorted stereo image, requires a small amount of data for storing or transmitting, and has high reliability. Especially in real-time communication system, the method can be utilized for monitoring perceived quality of the stereo image and adjusting the code rate thereof, so as to achieve better visual effects.